Pouch-type secondary battery

ABSTRACT

A pouch-type secondary battery including: an electrode assembly having a first electrode plate, a second electrode plate, and a separator disposed therebetween; and a pouch case including a first case part having a pouch to house the electrode assembly, a second case part disposed over an open end of the pouch, and sealing portions to seal the second case part to the first case part. The sealing portions include wing portions that are bent to cover opposing sides of the pouch, and bent portions that are bent from the wing portions, to cover a bottom surface of the pouch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/173,143, filed on Jul. 15, 2008, which claims the benefit of KoreanApplication No. 2007-72844 filed Jul. 20, 2007, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to a pouch-type secondarybattery including a pouch case having bent sealing portions, to coveredges of a battery cell, and to buffer external impacts.

2. Description of the Related Art

Generally, a lithium polymer battery refers to a battery including anelectrode assembly, which includes a separator disposed between apositive plate and a negative plate. The separator electrically isolatesthe plates, and includes an ion-conducting medium, i.e., an electrolyte.Such a separator is formed of a gel polymer that is impregnated with theelectrolyte, in order to improve ionic conductivity. The gel polymerelectrolyte provides various advantages, such as, excellent adhesion toelectrodes, superior mechanical properties, and ease of manufacturing,in addition to improved ionic conductivity.

A lithium polymer battery can be fabricated in the form of a plate-likestructure, so there is no need to adopt a winding process, which isnecessarily involved in manufacturing some lithium ion batteries. As aresult, the electrode assembly can be in the form of a stacked,plate-like structure, and it is also possible to fabricate the electrodeassembly as a square-shaped structure. Further, there is substantiallyno electrolyte exposed to the outside, due to an internal injection ofthe electrolyte into the cell, which is fabricated as an integralstructure. In addition, the electrode assembly can be processed into aplate-like structure, so there is no need to apply pressure to shape theelectrode assembly into a rectangular structure. Consequently, it ispossible to use a thin and flexible pouch case instead of a thicker,harder square-shaped, or cylindrical can to house the battery.

As discussed above, when the flexible pouch case is used, it is possibleto significantly reduce a thickness of the battery, as compared to usinga can. As a result, it is possible to form much larger numbers of theelectrode assemblies in the same volume. That is, the battery capacitycan be greatly increased. Further, due to the flexibility of the pouchcase, it is possible to easily fabricate the battery in a desired form.Therefore, the thus-fabricated battery is readily mounted in a varietyof electronic devices.

However, despite the increased battery capacity and shape-ability, apouch case suffers from problems associated with poor mechanicalstrength, and is thereby vulnerable to external impacts. In particular,when a large-area pouch-type secondary battery is dropped, a relativelygreater impact force is applied to edges of the battery. Impacts to theedges of the battery result in various problems, such as, tearing of thepouch case by the electrode assembly, and opening of sealing portions ofthe pouch case.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a pouch-type secondary batteryhaving a structure that is impact resistant.

Aspects of the present invention provide a pouch-type secondary batterycomprising: an electrode assembly including a first electrode plate, asecond electrode plate, and a separator disposed therebetween; and apouch case including a first case part having a pouch to house theelectrode assembly, and a second case part to seal the electrodeassembly in the first case part.

According to aspects of the present invention, the pouch case includessealing portions. The sealing portions include wing portions to coveropposing sides of the pouch, and bent portions to cover opposing edgesof the pouch.

According to aspects of the present invention, the bent portions may befolded around the edges of the pouch, such that the ends of the bentportions face each other, and partially cover a side of the pouch formedby the second case. The wing portions and bent portions can be generallyflat. The bent portions can be bent from the wing portions at asubstantially right angle (90°).

According to aspects of the present invention, spaces may be formedbetween the bent and wing portions, and the covered edges of the pouch.

According to aspects of the present invention, the wing portions may berounded, and the radius of curvature of the wing portions may be lessthan the radius of curvature of the edges of the pouch.

According to aspects of the present invention, the interface between thewing portions and the bent portions may be chamfered, and the wingportions may be rounded.

According to aspects of the present invention, the bent portions arecorrugated, include alternate convexities and concavities, and only thecentral portions of the concavities contact the pouch. The pouch casemay include a third case part to cover a bottom side of the pouch andportions of the wing portions.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1A is a schematic exploded perspective view of a pouch-typesecondary battery, in accordance with an exemplary embodiment of thepresent invention;

FIG. 1B is a plan view showing a partially assembled version of thesecondary battery of FIG. 1A, as viewed from the bottom;

FIG. 1C is a schematic perspective view of a pouch-type secondarybattery, in accordance with an exemplary embodiment of the presentinvention;

FIG. 1D is a cross-sectional view taken along line Ic-Ic of FIG. 1C;

FIG. 2 is a cross-sectional view of a pouch-type secondary battery, inaccordance with another exemplary embodiment of the present invention;

FIG. 3A is a schematic cross-sectional view of a pouch-type secondarybattery, in accordance with an exemplary embodiment of the presentinvention;

FIG. 3B is a cross-sectional view taken along line IIIb-IIIb of FIG. 3A;

FIG. 4 is a schematic perspective view of a pouch-type secondarybattery, in accordance with an exemplary embodiment of the presentinvention;

FIG. 5A is a schematic perspective view of a pouch-type secondarybattery, in accordance with an exemplary embodiment of the presentinvention; and

FIG. 5B is a cross-sectional view taken along line Vb-Vb of FIG. 5A.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The exemplary embodiments are described below, in order toexplain the aspects of the present invention, by referring to thefigures. Those skilled in the art will appreciate that variousmodifications, additions and substitutions are possible withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims. Unless otherwise defined, all technical andscientific terms used herein have the same meaning as commonlyunderstood, by one of ordinary skill in the art to which this inventionbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of thespecification and relevant art, and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.Well-known functions or constructions may not be described in detail forbrevity and/or clarity.

FIG. 1A is a schematic exploded perspective view of a pouch-typesecondary battery 100, in accordance with an exemplary embodiment of thepresent invention, and FIG. 1B is a plan view showing a partiallyassembled version of the secondary battery 100. Referring to FIGS. 1Aand 1B, the pouch-type secondary battery 100 includes: an electrodeassembly 10 including a positive plate 11, a negative plate 12, and aseparator 13 disposed therebetween; a pouch case 20 to house theelectrode assembly 10, comprising a first case part 21 and a second casepart 22 (first cover). The first case part 21 has a pouch 21 a toreceive the electrode assembly 10. The first and second case parts 21,22 are folded together, and then attached to one another, to secure theelectrode assembly 10 in the pouch case 20.

The positive plate 11 and the negative plate 12 include electrode activematerial layers (not shown) on surfaces of electrode current collectors(not shown). The separator 13 is impregnated in an organic electrolyte.The electrode assembly 10 is formed by winding the positive plate 11,the negative plate 12, and the separator 13 into a jelly roll-typestructure.

The positive plate 11 is fabricated by applying a positive electrodeactive material layer, containing a lithium-based oxide as a mainingredient, to both sides of a positive electrode current collectorformed of a thin aluminum foil. Both ends of the positive electrodecurrent collector are provided with positive electrode uncoated areas,on which the positive electrode active material layer is not coated.

The negative plate 12 is fabricated by applying a negative electrodeactive material layer, containing a carbon material as a mainingredient, to both sides of a negative electrode current collectorformed of a thin copper foil. Both ends of the negative electrodecurrent collector are provided with negative electrode uncoated areas,on which the negative electrode active material layer is not coated.

A positive electrode tap 15 is formed on one side of the positive plate11. A negative electrode tap 16 is formed on one side of the negativeplate 12. The positive electrode tap 15 and the negative electrode tap16 are arranged parallel to each other. Portions of the positiveelectrode tap 15 and the negative electrode tap 16 are exposed outsideof the pouch case 20, such that the electrode assembly 10 can beelectrically connected to an external device.

The positive electrode tap 15 and the negative electrode tap 16 aregenerally formed of a metal, such as aluminum, copper, or nickel, andshould have a sufficient electrical conductivity to minimize a voltagedrop. The positive electrode tap 15 and the negative electrode tap 16are large enough to accommodate a significant amount of an electriccurrent, at a low level of resistance. Generally, the positive electrodetap 15 is formed of aluminum and the negative electrode tap 16 is formedof nickel.

Insulating tapes 17 are disposed on portions of the electrode taps 15,16, which extend through the pouch case 20, when the pouch case 20 issealed. The insulating tapes 17 serve to prevent short-circuits betweenthe electrode taps 15, 16, and/or the pouch case 20.

The insulating tape 17 may be formed of a composite material havingexcellent insulating performance, heat-resistance, and durability. Morespecifically, the insulating tape 17 may be formed of a compositematerial in which an organic material layer (not shown) formed of aresin is mixed with an inorganic material (not shown), having a meltingpoint that is higher than that of the resin. Therefore, the insulatingtape 17 is capable of maintaining the insulating function, even when theorganic material layer is melted, and/or lost, due to high fusionbonding temperatures applied to seal the pouch case 20.

The pouch case 20 is divided into two parts, i.e., the first case part21 and the second case part 22, at the folding line F. The pouch 21 a isformed in the center of the first case part 21, via a conventionalmethod, such as, press-processing, or the like.

The pouch case 20 may be formed of a metal thin film, for example, analuminum thin film. An insulating layer of a resin, or nylon, may beformed on an outer surface of the pouch case 20, to protect the metalthin film from damage, and/or external electrical contacts.

A thermo-adhesive resin (not shown) of an organic material, such as,polypropylene, polyethylene, or the like can be coated onto an innersurface of the pouch 20. For example, a cast polypropylene (CPP) may beused as the adhesive resin. The CPP layer may be formed of a compositeof the organic material and inorganic material particles.

The pouch case 20 is sealed by folding the first case part 21 onto thesecond case part 22, then applying heat and pressure to fuse the CPPlayers formed on inner surfaces of the first case part 21 and the secondcase part 22. More specifically, the fusing forms sealing portions 25,26, 27, which extend around three sides of the pouch case 20.

FIG. 1C is a schematic perspective view of the pouch-type secondarybattery 100, after further processing in accordance with an exemplaryembodiment of the present invention, and FIG. 1D is a cross-sectionalview taken along line Ic-Ic of FIG. 1C. Referring to FIGS. 1C and 1D,the pouch-type secondary battery 100 is configured such that the sealingportions 25, 26 (shown in FIG. 1A) are bent around two opposing sides ofthe electrode assembly 10. More specifically, both sides of the pouch 21a are surrounded by the sealing portions 25, 26.

The sealing portions 25, 26 include wing portions 25 w, 26 w, and bentportions 25 e, 26 e, respectively. The wing portions 25 w, 26 w, arefolded, so as to cover opposing sides 21 a 2, 21 a 3 of the pouch 21 a.The bent portions 26 e, 25 e are folded away from the wing portions 25w, 26 w, to cover opposing edges 27 a, 27 b of the pouch 21 a, and topartially cover a bottom surface 21 a 1 of the pouch 21 a. As referredto herein, “bottom” and “top” surfaces are used for convenience, and donot limit the present teachings to any particular orientation.

According to aspects of the present embodiment, it is possible toachieve greater protection of the electrode assembly 10, because thesealing portions 25, 26 cover the edges 27 a, 27 b of the pouch 21 a,and the sides 21 a 2, 21 a 3 of the pouch 21 a. Therefore, it ispossible to absorb impacts applied to edges of the pouch-type secondarybattery 100. In particular, it is possible to enhance buffering effectsagainst impacts, in a case of large-area pouch-type secondary batteries,which generally have edges which are susceptible to relatively largeimpacts, when dropped.

Referring to FIG. 1D, the bent portions 25 e, 26 e extend from the wingportions 25 w, 26 w. The bent portions 26 e, 25 e are bent such thatends thereof face one another. In other words, the bent portions 25 e,26 e partially cover the bottom surface 21 a 1 of the pouch 21 a, andreinforce the corners 27 a, 27 b of the pouch 21 a. Therefore, the pouch21 a is further firmly supported, to prevent movement or shaking of theelectrode assembly 10 inside the pouch 21 a, which may occur uponapplication of external impacts. As a result, tearing of the pouch case20, or opening of the sealing portions 25, 26, may be prevented.

The bent portions 25 e, 26 e are bent to a substantially right angle(90°), with respect to the wing portions 25 w, 26 w. If the aforesaidangle is smaller than 90°, the buffering action may be decreased. On theother hand, if such an angle is larger than 90°, the pouch 21 a may notbe properly supported, which may result in tearing of the pouch, oropening of the sealing portions 25, 26, if the pouch-type secondarybattery 100 is impacted.

FIG. 2 is a cross-sectional view of a pouch-type secondary battery 200,in accordance with another exemplary embodiment of the presentinvention. Referring to FIG. 2, the pouch-type secondary battery 200includes wing portions 31 w, 32 w and bent portions 31 e, 32 e that arebent from the wing portions 31 w, 32 w. The bent portions 31 e, 32 ediffer from the bent portions 25 e, 26 e, of the pouch-type secondarybattery 100.

Folds 38 a, 38 b, are formed between the bent portions 31 e, 32 e andthe wing portions 31 w, 32 w, and are spaced at a given distance fromedges 27 a, 27 b of a pouch 21 a. That is, air cushions 30 to absorbimpacts are formed between the folds 38 a, 38 b and the edges 27 a, 27b.

The folds 38 a, 38 b, may be rounded by a rounding process. Thecurvature radius of the folds 38 a, 38 b is set to be smaller than thatof the edges 27 a, 27 b. If the curvature radius of the folds 38 a, 38 bis larger than that of the edges 27 a, 27 b, the folds 38 a, 38 b willcontact the edges 27 a, 27 b, such that the air cushions 30 are notformed.

Even though not shown in FIG. 2, the folds 38 a, 38 b may be formed by achamfering process, rather than the rounding process. That is, the folds38 a, 38 b may be formed to have a rounded or chamfered structure. Asmentioned above, due to the formation of the air cushions 30 between theedges 27 a, 27 b and the folds 38 a, 38 b, the pouch-type secondarybattery 200 can further reduce damage, due to impacts applied to thepouch-type secondary battery 200.

FIG. 3A is a schematic cross-sectional view of a pouch-type secondarybattery 300, in accordance with another exemplary embodiment of thepresent invention, and FIG. 3B is a cross-sectional view taken alongline IIIb-IIIb of FIG. 3A. The pouch-type secondary battery 300 isconfigured to have a pouch 41 a and wing portions 41 w, 42 w that aredifferent from those of the previous exemplary embodiments. The battery300 also includes bent portions 41 e, 42 e that extend from the wingportions 41 w, 42 w, onto the bottom of the pouch 41 a.

Referring to FIGS. 3A and 3B, the wing portions 41 w, 42 w and opposingsides 41 a 2 of the pouch 41 a are subjected to a rounding process, suchthat the wing portions 41 w, 42 w are rounded to match the curvature ofthe sides 41 a 2 of the pouch 41 a. More specifically, edges of the wingportions 41 w, 42 w and corresponding edges 47 of the pouch 41 a arecurved, such that there is no separation between the wing portions 41 w,42 w and the sides 41 a 2 of a pouch 41 a. As a result, the wingportions 41 w, 42 w can absorb additional impact energy. The curvatureof the wing portions 41 w, 42 w allows for the size of the pouch 41 a tobe increased, which allows for a larger electrode assembly 10 to bereceived therein, thereby further enhancing a capacity of the secondarybattery 300.

FIG. 4 is a schematic perspective view of a pouch-type secondary battery400, in accordance with an exemplary embodiment of the presentinvention. The pouch-type secondary battery 400 is configured to havedifferent bent portions 51 e, 52 e than the previous embodiments.

Referring to FIG. 4, the bent portions 51 e, 52 e are corrugated withrepeating convexities 51 e′ and concavities 51 e″. Only the centralportions of concavities 51 e″ contact a bottom surface 51 a 1 of a pouch51 a. As a result, it is possible to further increase the absorption ofimpacts, which consequently further improves the stability of thepouch-type secondary battery 400.

FIG. 5A is a schematic perspective view of a pouch-type secondarybattery 500, in accordance with yet another exemplary embodiment of thepresent invention, and FIG. 5B is a cross-sectional view taken alongline Vb-Vb of FIG. 5A.

Referring to FIGS. 5A and 5B, the pouch-type secondary battery 500includes a third case 60 (second cover), which is disposed upon an uppersurface 22 s of the secondary battery 500. The third case covers edges29 a, 29 b of the secondary battery 500. Therefore, edges 27 a, 27 b, 29a, 29 b of the secondary battery 500 are supported, by the bent portions25 e, 26 e and the third case 60, thereby further enhancingimpact-alleviating effects on the edges.

As is apparent from the above description, the present invention canenhance buffering effects against impacts, even in a large-areapouch-type secondary battery, which is susceptible to relatively greaterimpact on edges of the battery. Seal portions support a pouch of a pouchcase, and prevent the tearing and/or opening of the pouch case.

Although a few exemplary embodiments of the present invention have beenshown and described, it would be appreciated by those skilled in the artthat changes may be made in these embodiments, without departing fromthe principles and spirit of the invention, the scope of which isdefined in the claims and their equivalents.

1. A pouch-type secondary battery, comprising: an electrode assemblycomprising a first electrode plate, a second electrode plate and aseparator disposed between the first electrode plate and the secondelectrode plate; and a pouch case comprising, a pouch having a bottomand opposing sides, to house the electrode assembly, a first coverdisposed upon the opposing sides of the pouch, and sealing portions toseal the first cover to the pouch, wherein the sealing portions comprisewing portions that are folded toward the pouch, so as to cover theopposing sides of the pouch, and bent portions that extend from the wingportions, so as to partially cover the bottom of the pouch, and whereinthe wing portions have rounded edges and the wing portions are roundedto match a curvature of the sides of the pouch.
 2. The battery accordingto claim 1, wherein the opposing sides of the pouch are rounded.
 3. Thebattery according to claim 1, wherein the opposing sides of the pouchhave rounded edges and the rounded edges of the wing portions face therounded edges of the opposing sides of the pouch.
 4. The batteryaccording to claim 3, wherein there is no separation between the roundededges of the wing portions and the rounded edges of the opposing sidesof the pouch.
 5. The battery according to claim 1, wherein the shape ofthe wing portions matches the shape of the opposing sides of the pouch,such that there is substantially no separation between the wing portionsand the opposing sides of the pouch.
 6. The battery according to claim3, wherein the rounded edges of the wing portions have smaller radii ofcurvature than the rounded edges of the opposing sides of the pouch. 7.The battery according to claim 1, wherein the bent portions arecorrugated.